The present invention relates in general to a mechanical stop mechanism. More particularly, this invention concerns a precision stop mechanism for use with machinery in which an elongate workpiece is indexed through one or more stations at which various tooling operations are performed.
In automatic or semiautomatic tooling operations, it is extremely important that the workpiece be properly positioned prior to the tooling operation. The problem of properly positioning a workpiece becomes even greater in machinery of the type wherein an elongate workpiece or length of bar stock is incrementally advanced through one or more tooling stations. For example, consider the situation when an extended length of extruded aluminum stock is tooled into a number of relatively smaller pieces, such as frame sections for windows, doors and the like. During this process, the workpiece must be indexed accurately from station to station to achieve the necessary precision, as well as to miminize material waste and therefore expense. The problem of accurately indexing a workpiece is particularly critical when it is subjected to numerous advancements over short distances to produce a large number of relatively small components. The prior art includes various forms of stop mechanisms which have been employed in this indexing function. However, the stop mechanisms heretofore available have been found to be either precise but expensive and lacking in durability, or durable but lacking in precision. There is thus a need for an improved stop mechanism of rugged constuction and precise operation.
The present invention comprises an improved stop mechanism which overcomes the foregoing and other problems associated with the prior art. According to the broader aspects of the invention, there is provided an improved stop mechanism for use with machinery wherein an elongate workpiece is advanced incrementally through one or more tooling stations. The invention includes an arm mounted for limited pivotal movement about first and second axes and between ready and stop positions. In the ready position, the arm is biased into sliding contact with the workpiece. Upon engagement with a notch or other locating surface on the workpiece, the arm is moved to the stop position to halt movement of the workpiece and simultaneously actuate a switch or valve controlling the desired tooling operations. The arm is then disengaged from the workpiece and returned to the ready position permitting advancement of the workpiece again. The invention is characterized by precise operation and durable construction.
In accordance with more specific aspects of the invention, an improved stop mechanism includes an arm having front and back ends. The arm is mounted in a groove on a block by means of a single pin received through an aperture comprising two coaxial conical bores formed in opposite sides of the arm. Predetermined walls of the groove are angled to permit limited pivotal movement of the arm between a ready position and a stop position. Springs are positioned in bores provided in the block to bias the front end of the arm into contact with the workpiece and in a direction opposite to movement of the workpiece. In one embodiment of the stop mechanism, the arm is biased into sliding contact with the upper side of the workpiece, while the arm is biased into contact with the under side of the workpiece in another embodiment of the invention. Upon engagement with a predetermined notch or locating surface on the workpiece, the arm pivots therewith until reaching the stop position. In the stop position, the workpiece is held in positive interfering engagement with the front end of the arm while the back end of the arm actuates a control device to generate a predetermined signal for initiating desired tooling operations on the stationary work piece. The arm is subsequently disengaged from the workpiece with a double-acting cylinder mounted adjacent to the stop mechanism. The workpiece is thereby released for movement and the arm is returned to the ready position by the springs. The stop mechanism of the invention can be employed in automatic or semiautomatic machine tools of the type wherein an extended workpiece, such as a length of extruded aluminum, is incrementally advanced through stations performing notching, cutting, drilling, punching, perforating or other tooling operations to the workpiece between advancements thereof.